proposed for determining long-term properties for FRP rebars based on the Arrhenius accelerated aging procedure (Bank et al. 2003). Test methods for determining the properties of FRP rebars can be found in JSCE (1997) and in ACI 440.3R-04 (2004).

FRP rebars should only be used at service temperatures below the glass transition temperature of the polymer resin system used in the bar. For typical vinylester polymers this is around 200° F. The bond properties have been shown to be highly dependent on the glass transition temperature of the polymer (Katz et al. 1999). In addition, it is important to note that the coefficients of thermal expansion of FRP rebars are not the same in the transverse (radial) direction as in the longitudinal direction. The coefficient of thermal expansion may be close to an order of magnitude higher in the transverse direction of the bar due to its anisotropic properties (see typical properties in Table 16.4). This may cause longitudinal splitting in the concrete at elevated temperatures if insufficient cover is not provided.

FRP rebars containing glass fibers can fail catastrophically under sustained load at stresses significantly lower than their tensile strengths, a phenomenon known as creep rupture or static fatigue. The amount of sustained load on FRP rebars is therefore limited by design guides.

FRP reinforcing bars made of thermosetting polymers (e.g., vinylester, epoxy) cannot be bent in the field and must be produced by the FRP rebar manufacturer with ''bends'' for anchorages or stirrups. The strength of the FRP rebar at the bend is substantially reduced and must be considered in the design.

FRP rebars should not be used for carrying compressive stress in concrete members (i.e., compression reinforcement) where they are used in the compression zone they should be suitably confined to prevent local instability.